There are many distinctive industries within the metals art. Entire industries are based on various metallurgical products: high temperature resistant alloys (superalloys), corrosion-resistant alloys, wear-resistant alloys, and the like. These products are not readily interchangeable because each has a certain set of inherent properties that are not found in other products. For example, superalloys are strong at high temperature but are notoriously subject to wear. Corrosion-resistant alloys have excellent resistance to wet corrosion exposure but are generally subject to wear and are low in strength. Wear-resistant alloys are superior under erosion and wear conditions but are generally brittle and most of them do not offer appreciable corrosion resistance.
By way of composition, superalloys may be nickel and/or cobalt base; corrosion-resistant alloys are generally nickel base; and wear-resistant alloys are usually cobalt base.
Furthermore, the metallurgical structures of these alloys generally vary depending upon the required properties. Superalloys are known to have a strong solid solution matrix which may be dispersed with gamma prime. Corrosion-resistant alloys generally have a solid solution matrix and are free of precipitates, i.e., carbides. Wear-resistant alloys must depend upon a high content of precipitates, especially carbides, to provide the wear properties.
Much research has been directed toward the improvement of cobalt-base alloys. The pioneer invention of cobalt-base superalloys was disclosed by Elwood Haynes in U.S. Pat. No. 873,745 (Dec. 17, 1907) followed by his subsequent U.S. Pat. Nos. 1,057,423; 1,057,828; and 1,150,113. These alloys were generally used as cutting tools, utensils and the like implements. Later, cobalt-base alloys were modified by Austenal Laboratories under the now Howmedica trademark VITALLIUM.RTM. for use as cast dentures as taught in U.S. Pat. Nos. 1,958,446, 2,135,600, and 4,514,359 and also for use as components of gas turbine engines as taught in U.S. Pat. No. 2,381,459.
A wrought or cast cobalt-base alloy was disclosed in U.S. Pat. No. 2,704,250. The alloy known in the art as Alloy 25, has adequate corrosion resistance but has relatively poor wear (erosion) resistance. U.S. Pat. Nos. 3,865,585 and 3,728,495 disclose a nickel -free alloy with high nitrogen and carbon contents for use as dental prostheses articles. U.S. Pat. No. 2,486,576 relates to a novel heat-treating process for cobalt-base alloys. Disclosed are several cobalt chromium alloys containing manganese, nickel and molybdenum. U.S. Pat. No. 3,237,441 discloses a cobalt-base alloy for use as a tube rolling mill plug. The alloy has a high carbon content and is nitrogen free.
The Pfizer Hospital Products Group Inc. has recently made improvements in the VITALLIUM.RTM. alloys mentioned hereinabove. The alloys are made by an oxide dispersion process as disclosed in U.S. Pat. Nos. 4,714,468; 4,668,290, 4,631,290 corresponding to European Patent Application No. 0-195,513.
The patents mentioned above, of course, are only a small portion of the extensive research and development of cobalt-base alloys over the past 75 years. Each invention provided improvements in a limited number of engineering properties in strength, corrosion resistance and/or wear resistance. In the present industrial world, there is an urgent need for alloys with higher strength, capable of operating under more severe corrosive and wear conditions.